Steam generator having at least one combustion chamber for burning solid, liquid and/or gaseous fuels

ABSTRACT

Steam generator includes a watertube boiler having an upper and lower drum, a plurality of steam tubes extending between the drums and surrounding and defining a forward and rearward radiation chamber, and means for alternately and simultaneously burning solid, liquid and gaseous fuels for heating the boiler comprising a cylindrical tornado-flow combustion chamber disposed in a lower region of the boiler at an axial end thereof, the tornado-flow combustion chamber being lined with part of the steam tubes defining the radiation chambers and having tangential nozzles for feeding combustion air and fluid fuel thereto, the tornado-flow combustion chamber also having a burner and a conically outwardly flaring combustion gas outlet extending into the forward radiation chamber located at an axial end thereof, solid particulate fuel-burning additional combustion chamber lined with water tubes and located outside the boiler and adjacent the tornado-flow combustion chamber, the additional combustion chamber having a combustion gas line extending from the top thereof and communicating with the radiation chambers and further having a gas outlet communicating with the tornado-flow combustion chamber burner.

United States Patent [191 Agrest 1 June 5,1973

[54] STEAM GENERATOR HAVING AT LEAST ONE COMBUSTION CHAMBER FOR BURNING SOLID, LIQUID AND/OR GASEOUS FUELS [76] Inventor: Jacobo Agrest, Avda Belgrano 355,

Buenos Aires, Argentina [22] Filed: Apr. 16, 1971 [21] Appl. No.: 134,745

[30] Foreign Application Priority Data Primary ExaminerKenneth W. Sprague Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [57] ABSTRACT Steam generator includes a watertube boiler having an upper and lower drum, a plurality of steam tubes extending between the drums and surrounding and defining a forward and rearward radiation chamber, and means for alternately and simultaneously burning solid, liquid and gaseous fuels for heating the boiler comprising a cylindrical tornado-flow combustion chamber disposed in a lower region of the boiler at an axial end thereof, the tornado-flow combustion chamber being lined with part of the steam tubes defining the radiation chambers and having tangential nozzles for feeding combustion air and fluid fuel thereto, the tornado-flow combustion chamber also having a burner and a conically outwardly flaring combustion gas outlet extending into the forward radiation chamber located at an axial end thereof, solid particulate fuel-burning additional combustion chamber lined with water tubes and located outside the boiler and adjacent the tornado-flow combustion chamber, the additional combustion chamber having a combustion gas line extending from the top thereof and communicating with the radiation chambers and further having a gas outlet communicating with the tornado-flow combustion chamber burner.

5 Claims, 7 Drawing Figures PAIENTEDJUN 5 i975 SHEET 10F 2 STEAM GENERATOR HAVING AT LEAST ONE COMBUSTION CHAMBER FOR BURNING SOLID, LIQUID AND/OR GASEOUS FUELS My invention relates to steam generator having at least one combustion chamber for burning solid, liquid and/or gaseous fuels, and more particularly to such steam generator having a water-tube boiler provided with a radiation chamber that is enclosed or defined by steam tubes extending between an upper and a lower drum.

In conventional steam generators, difficulties are encountered in forming combustion chambers so that solid liquid or gaseous fuels are burnable therein simultaneously or alternately with the same efficiency and economy. Particular difficulties are produced when the construction calls for integration of the combustion chamber and the steam generator per se.

Flame development is not promoted, however, by the generally parallelepipedal shape of the combustion chambers of conventional steam generators because they do not conform and are not accommodated to the aerodynamics of the combustion chambers. It is therefore necessary to produce theoretically overdimensioned combustion chambers in order to maintain combustion to an economic degree before the combustion gases leave the combustion chambers.

On the other hand, due to the geometry of the combustion chambers, only a non-uniform distribution especially of the radiating heat is possible over the entire endothermic or heat-absorbing surface, because the absorbed radiant heat is a function of the angle within which each sector of the combustion chamber lies with respect to the flame body proper. Due to this nonuniform distribution, low mean values of the radiation intensity must be assumed per unit area of the heatabsorbing walls in order to reliably avoid film vaporizing conditions which would otherwise cause tube burn up. This leads to greatly over-dimensioned radiant heating surfaces causing considerable increase in total costs of the installation.

Due to this over-dimensioning of the combustion chambers, on the other hand, the probability of total combustion of the coal or other fuel particles is reduced. The efficiency of combustion is thereby lowered and, on the other hand, the problem of air pollution is thereby increased, so that final separators or precipitators are required, which call for additional technical and economic expense.

Furthermore, the distribution of isotherms along the path of the gas shows very high peaks in the vicinity of the zones of the openings through which fuel and air are axially fed to the combustion chamber and a decline thereof in proportion as the released heat is absorbed by the surrounding radiant heating surfaces. The ash resulting from the combustion is therefore exposed to temperatures that are higher than necessary for softening, melting and draining off the ash. Furthermore, vaporization of volatile or fugitive components thereof takes place, so that slags which are difficult to remove, then deposit in after-connected colder heating surfaces located farther downstream in the path of the combustion gas through the steam generator. In addition, the shape ofthe combustion gas path is unsatisfactory for separating the entrained ash and soot and therefore compels a further reduction in the velocity of the gas so as to moderate entrainment and erosive effect.

These considerations apply essentially to the radiation zones, however similar problems occur in the convection zone wherein still a greater temperature drop of the combustion gas can have negative effects. it is therefore important that the flow of the combustion gas along the entire length of the convection zone is directed perpendicularly to the tube bundles so that the fine fly ash readily falls off and can be withdrawn. In any other situation, the fly ash will deposit between the tubes and form an insulating layer so that heat transfer is thereby considerably impaired.

Solutions for these problems have already been proposed in Argentine Pat. Nos. 147,736 and 151,173 wherein however, there is no concern with an integrated construction of steam boilers and combustion chambers but rather with separate devices having very good coordination with one another.

Additional difficulties are produced, however, in the case of integrated construction wherein, on the one hand, optimal space utilization is in fact assured but, on the other hand, special care must be given, however, to the flow guidance and to the disposition of the individual combustion chambers.

It is accordingly an object of my invention to provide steam generator having at least one combustion chamber for burning solid, liquid and/or gaseous fuel which avoids the aforementioned difficulties of the heretofore known steam generators of this general type. More specifically, it is an object of my invention to provide such steam generator as an integrated construction wherein solid, liquid and gaseous fuel may be burned simultaneously or alternately, in fine-grain or lumpy form, and wherein virtually total burning of the fuel and minimal yield of ash are produced.

With the foregoing and other objects in view, there is provided in accordance with the invention, in a steam generator, a water-tube boiler comprising an upper and a lower drum, a plurality of steam tubes extending between the upper and lower drums and surrounding and defining a forward and rearward radiation chamber, and means for alternately and simultaneously burning solid, liquid an gaseous fuels for heating the boiler comprising a cylindrical tornado-flow combustion chamber disposed in a lower region of the water-tube boiler at an axial end thereof, the tornado-flow combustion chamber being lined with part of the steam tubes defining the radiation chambers and having tangentially disposed nozzles for feeding combustion air and fluid fuel thereto, the tornado-flow combustion chamber also having a burner and a conically outwardly flaring combustion gas outlet located at an axial end of the tornado-flow combustion chamber and axially extending into the forward radiation chamber and an additional combustion chamber for burning solid particulate fuel, the additional combustion chamber being lined with water tubes and being located outside the water-tube boiler and adjacent the tornado-flow combustion chamber, the additional combustion chamber having a combustion gas line extending from the top thereof and communicating with the radiation chambers and further having a gas outlet communicating with the burner of the tornado-flow combustion chamber.

The tornado-flow combustion chamber employed in the steam generator of my invention utilizes the special properties ofa circulatory fluid flow having the character of a rotational flow as it occurs in tornadoes, hence the use of the designation tornado flow" for the phenomena involved therein. For further details regarding such tornado-flow combustion chamber, reference may be had particularly to U.S. Pat. No. 3,372,678 of K. R. Schmidt, issued Mar. 12, 1968. Other details regarding the theory, operation and applications of the tornadoflow principle may be obtained from US. Pat. Nos. 3,199,268 to No. 3,199,272 and No. 3,226,165, for example.

In accordance With another feature of the invention, the burner of the tornado-flow combustion chamber has a tangentially disposed inlet for feeding combustion air and fine grain fuel therethrough. Moreover, additional tangentially disposed inlets for fine-grain fuel are formed in the tornado-flow combustion chamber proper.

In accordance with a further feature of the invention and to improve the combustion, air nozzles communicating with the gas outlet are disposed in an array in the tornado-flow combustion chamber coaxial to the gas outlet.

In accordance with an added feature of the invention, another burner for gaseous or liquid fuel is disposed in the forward radiation chamber.

In accordance with additional features of the invention, an inner layer of the steam tubes surrounding and defining the radiation chambers is densely packed and, in the space between the inner layer of the steam tubes and an outer wall of the water-tube boiler, less densely packed steam tubes are disposed so as to be heated by convection. Furthermore, in the space between the inner layer of the steam tubes and the outer wall of the boiler, a combustion gas inlet is disposed in a region adjacent a rearward wall of the boiler.

By means of this arrangement and division of the burner system of the steam generator of the invention into more than one burner, it is possible, on the one hand, to burn gaseous, liquid and solid fuels simultaneously while still attaining, due to the integrated and compact construction, maximum efficiency and economy for the entire assembly.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in steam generator having at least one combustion chamber for burning solid, liquid and- /or gaseous fuels, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

FIG. 1 is a diagrammatic longitudinal sectional view of the steam generator of the invention;

FIG. 2 is a cross-sectional view of FIG. 1 taken along the line II II in the direction of the arrows;

FIG. 3 is a cross-sectional view of FIG. 1 taken along the III III in the direction of the arrows;

FIG. 4 is a longitudinal sectional view taken horizontally through the steam generator of FIG. 1, along the line IV IV in the direction of the arrows;

FIG. 5 is a longitudinal sectional view taken horizontally through the steam generator of FIG. 1 along the line V V in the direction of the arrows;

FIG. 6 is a fragmentary enlarged cross-sectional view of a tornado-flow burner forming part of the steam generator of FIG. 1; and

FIG. 7 is a fragmentary enlarged cross-sectional view of a combustion chamber connected to the steam generator of FIG. 1 at a location thereof in the vicinity of the ash outlet therefor.

Referring now to the drawing, and first particularly to FIGS. 1, 2 and 3 thereof, the steam generator of the invention includes a water-tube boiler formed of an upper drum 1, a lower drum 2 and a number of water tubes 3', 3", connecting both drums 1 and 2 to one another. The water tubes 3' are disposed in such manner as to define a forward radiation chamber 37, and the water tubes 3" are disposed so as to define a rearward radiation chamber 36, Tubes 35 are located in the convection zone between the interior densely packed rows of tubes 3' and 3", on the one hand, and the outer wall 4 of the water-tube boiler. In the rearward region of the radiation chamber 36 bordering on the end wall 4" thereof, a cylindrical tornado-flow combustion chamber 10 is located, in accordance with the invention, above the lower drum 2. As is apparent especially from FIG. 2, the water tubes 3" of the radiation chamber 36 extend into the tornado-flow combustion chamber 10 and form therein the lining of the combustion chamber. The tornado-flow combustion chamber 10 has, at the rear end thereof, an axial inlet opening 1 l for fine-grain fuel that is entrained by an air current directed therethrough. Such fuel can also be admitted directly into the combustion chamber 10 through tangential openings 13. The tornado-flow combustion chamber 10, at the forward end thereof, narrows down in the shape of a coaxial frustrum of a cone 12, that is formed generally by part of the tubes 3" and 35. The combustion gases in the forward radiation chamber 37 discharge through this downwardly tapering frustrum of a cone 12. Combustion air is admitted through nozzles 32 from air chambers 31 to the tornado-flow combustion chamber 10. Moreover, combustion air is also delivered to the tornado-flow combustion chamber 10 through axially extending nozzles 15 and tangentially disposed nozzles 15', which extend from an annular channel 14 surrounding the frustoconical outlet 12, the annular channel 14 being, in turn, in communication with the air supply chambers 31.

Adjacent the burner opening of the tornado-flow combustion chamber 10, there is located outside the water-tube boiler 4 proper, an additional combustion chamber 20, which is provided in the interior thereof with a wall of water tubes 21. The water tubes 21 are connected to a lower collector or header 22 and an upper collector or header 23 which are, in turn, connected respectively to the upper and lower drums 1 and 2.

The additional combustion chamber 20 has a generally prismatic cross section and is supplied through an inlet opening with relatively large chunks or particles of solid fuel, whereby, due to a valve-like construction 24' of the inlet opening 24, escape of gas is avoided. The combustion chamber 20, in the upper part thereof, is connected by a combustion gas line 25 with the rearward radiation chamber 36 so that the hot combustion gas can be used additionally for heating the water-tube boiler 4. The connection between the combustion chamber 20 and the tornado-flow combustion chamber proper is formed by an inlet 11, in which there is disposed additionally a feeding device for fine-grain fuel, shown in greater detail in FIG. 6. The fuel and combustion air are accordingly fed through a tangentially disposed supply duct 16 to the inlet opening 11 so that a tornado-flow is formed in the inlet opening 11.

In order to be able to burn fluidized or fluid fuel in pulverized or atomized form additionally in the steam generator, a further burner 26 is located in the inlet opening 11 to the tornado-flow combustion chamber 10, and a burner 17 is provided in the forward radiation chamber 37. Moreover, at the forward end face 4' of the water-tube boiler 4, tightly closing doors l8 and an ash discharge system 19 are provided, which are supplemented by a pouring guide 19'. The rearward end wall 4" of the water-tube boiler 4 is furnished with a door 27 which can also be supplemented with an ash discharge device if desired.

In order to protect the endangered components of the steam generator from a premature combustion, the air tube 33 for the additional combustion chamber 20 is, for example, enclosed by a water tube 30, as shown in FIG. 7, which also encloses the pouring guide 33.

The operation of the steam generator of the invention is as follows:

The water-tube boiler 4 is initially ignited with the frontally disposed conventional burner 17 or by means of the burner 26 of known type by injecting a spray of fluid fuel. After this first step, or in place thereof, the tornado-flow combustion chamber 10 can be set in operation by feeding atomized, pulverized or finely granulated fuel into the same through the tangentially disposed nozzles 13. Simultaneously, a mixture of air and fuel in fine-grain form can be blown through the line 16 into the tornado-flow combustion chamber 10. This air-fuel mixture, when entering through the feed opening 11, follows the path of the gases produced by the burner 26.

Simultaneously, or instead of the aforedescribed steps, the additional combustion chamber 20 can be set in operation by feeding solid, chunky or particulate fuel through the opening 24 and effecting ignition in a conventional manner. Accordingly, the water-tube boiler 4 can be set and maintained in operation with all types of fuel employed alternatingly or simultaneously.

In each case, the combustion gases take the same path through the steam generator of the invention. After the combustion gases leave the tornado-flow combustion chamber 10 through the outlet 12, they follow a path curving through 180 in upward direction as represented by the arrow 28 in FIG. 1, thereby initially heating the tubes 3' of the first radiation chamber 37 and thereafter the tubes 3" of the second radiation chamber 36. As shown in FIG. 5, the fumes or combustion gases divide into two branches, as shown by the arrow 29 in FIG. 5, in front of the rear end wall 4" of the water-tube boiler 4, both of the branches of flow, after turning through an arc of 180, then flowing in reverse direction through the convective tube groups 35. At the end of the convection zone in the reverse flow direction of the combustion gases, at the forward end wall 4' of the water-tube boiler 4, the combustion gases leave the water-tube boiler 4 through outlets 34 and a non-illustrated flue or smoke-stack.

Although the fuel is largely burned out due to the shape of the tornado-flow combustion chamber and the special blown-in introduction of fuel and combustion air, entrained ash is nevertheless deposited in the radiation chambers 37 and 36, due to the large volumes of the radiation chambers and the changes in direction accordingly, taken by the entrained ash therethrough. The deposited ash can then be removed by the discharging worm or screw conveyor 19 or the door 27 in the rear end wall 4".

The drawing shows but one embodiment of the steam generator of the invention. Numerous variations in individual features or details according to the aforedescribed embodiment are possible, however, within the scope of the invention. Thus, for example, guide plates or baffles for the combustion gases can be disposed in the convection zone between the tube rows 35. Furthermore, the additional combustion chamber 20 can be provided at a location other than the one in the illustrated embodiment, just as long as the sole condition is met that the combustion gas line 25 and the inlet opening 11 for the combustion gases of the tornado-flow combustion chamber 10 open into the water-tube boiler 4 proper. Moreover, the drums 1 and 2 can also be replaced by multiple drums, respectively.

The aforedescribed steam generator of the invention, on the whole, presents an exceptionally compact structural form with integrated combustion chambers which afford optimal combustion of the most varied fuels. Moreover, the combustion gas is guided in such manner that optimal utilization of the heat and transfer of the heat to the water tubes, is assured.

I claim:

1. In a steam generator, a water-tube boiler comprising an upper and a lower drum, a plurality of steam tubes extending between said upper and lower drums and surrounding and defining a forward and a rearward radiation chamber, and means for alternately and simultaneously burning solid, liquid and gaseous fuels for heating said boiler comprising a cylindrical tornadoflow combustion chamber disposed in a lower region of said water-tube boiler at an axial end thereof, said tornado-flow combustion chamber being lined with part of the steam tubes defining said radiation chambers and having tangentially disposed nozzles for feeding combustion air and fluid fuel thereto, said tornado-flow combustion chamber also having a burner and a conically outwardly flaring combustion gas outlet located at an axial end of the tornado-flow combustion chamber and axially extending into said forward radiation chamber, and an additional combustion chamber for burning solid particulate fuel, said additional combustion chamber being lined with water-tubes and being located outside said water-tube boiler and adjacent said tornadoflow combustion chamber, said additional combustion chamber having a combustion gas line extending from the top thereof and communicating with said radiation chambers and further having a gas outlet communicating with the burner of said tornado-flow combustion chamber.

2. Steam generator according to claim 1 wherein said burner of said tornadoflow combustion chamber has a tangentially disposed inlet for supplying combustion air and fine-grain fuel therethrough.

3. Steam generator according to claim 1 including a plurality of air nozzles communicating with said gas outlet of said tornado-flow combustion chamber, said thereof, said inner layer of steam tubes being spaced from an outer wall of said water-tube boiler and, in the space between said inner layer of steam tubes and said outer wall, a plurality of less densely packed steam tubes are disposed, as well as a combustion gas inlet lo cated in a region of said space adjacent a rearward wall of said water-tube boiler.

* t t t IIK 

1. In a steam generator, a water-tube boiler comprising an upper and a lower drum, a plurality of steam tubes extending between said upper and lower drums and surrounding and defining a forward and a rearward radiation chamber, and means for alternately and simultaneously burning solid, liquid and gaseous fuels for heating said boiler comprising a cylindrical tornado-flow combustion chamber disposed in a lower region of said water-tube boiler at an axial end thereof, said tornado-flow combustion chamber being lined with part of the steam tubes defining said radiation chambers and having tangentially disposed nozzles for feeding combustion air and fluid fuel thereto, said tornado-flow combustion chamber also having a burner and a conically outwardly flaring combustion gas outlet located at an axial end of the tornado-flow combustion chamber and axially extending into said forward radiation chamber, and an additional combustion chamber for burning solid particulate fuel, said additional combustion chamber being lined with water-tubes and being located outside said water-tube boiler and adjacent said tornado-flow combustion chamber, said additional combustion chamber having a combustion gas line extending from the top thereof and communicating with said radiation chambers and further having a gas outlet communicating with the burner of said tornado-flow combustion chamber.
 2. Steam generator according to claim 1 wherein said burner of said tornado-flow combustion chamber has a tangentially disposed inlet for supplying combustion air and fine-grain fuel therethrough.
 3. Steam generator according to claim 1 including a plurality of air nozzles communicating with said gas outlet of said tornado-flow combustion chamber, said air nozzles being disposed in said tornado-flow combustion chamber in an array coaxial to said gas outlet.
 4. Steam generator according to claim 1 including an additional burner of fluid fuel located in said forward radiation chamber.
 5. Steam generator according to claim 1 wherein said steam tubes surrounding and defining said radiation chambers include a more densely packed inner layer thereof, said inner layer of steam tubes being spaced from an outer wall of said water-tube boiler and, in the space between said inner layer of steam tubes and said outer wall, a plurality of less densely packed steam tubes are disposed, as well as a combustion gas inlet located in a region of said space adjacent a rearward wall of said water-tube boiler. 